For me it seems to be the old problem in MFN free, that highway=unclassified, which are the lowest level of settlement connecting roads in OSM, are put together with residential and lower to small local roads in MFN. For me that's irritating users and generates routing like the upper one.There was a thread about that before, but nothing happened. On countryside it's often the best to use these unclassified between settlements. So please change that in MFN-classification and you'll get some more totally satisfied users.

I agree with @hurdygurdyman. This has already been discussed extensively in 2 long threads.

It has come up as (new) user questions multiple times.

The best option is to split it.

the second best option is to enable them but not with the default 50% priority but with 40% or so. That is exactly how I use them. Sometimes it is the only possible way to use these roads.

Secondly: lots and lots of roads in cities fall into this category which means that Navigator uses completely unnecessary deviations because it does not use these roads. (But now I'm repeating some of the arguments which have been mentioned multiple times).

It might be a good idea to have two car profiles, one with local roads enabled and the other one with local roads disabled and see the difference in the route. If there is a lot of difference, like in efred's case, I would investigate with google maps/street view to make sure my car can make it.

In my experience a 'small local road' can be a very good road, wide, well paved and very easy to drive onto, or a very narrow passage, barely good for cycling or walking.